Method of preserving steel plate from corrosion and preparing elements of container bodies therefrom



Oct. 16, 1945. F. J. O'BRIEN ETAL 2,386,813

METHOD OF PRESERVING STEEL PLATE FROM CORROSION AND PREPARING ELEMENTSOF CONTAINER BODIES THEREFROM Filed July 21, 1942 wry/Z Q 3001 362x744[QM/Iva 675p ,BH/r/A/G 6 TP V LS'aAaM/AM:

/ J'TEP Qwuwwtow $7M} 6 0M Patented Oct. 16, 1945 METHOD OF PRESERVINGSTEEL PLATE FROM CORROSION AND PREPARING ELE- MENTS OF CONTAINER BODIESTHERE- FROM Frank J. OBrien, Pelham, N. Y., and Curtis E. Maier,Elmhurst, Ill., assignors to Continental Can Company, Inc., New York, N.Y., a corporation of New York Application July 21, 1942, Serial No.451,756

1 Claim.

The invention generally concerns the preparation of container elementsfrom steel plate and having a protective coating which will permiteflicient solder-bonding of seams.

Tin and terne plate container elements have i been employed forpackaging food product and other substances such as oils, powders, etc.;and such plates have been lacquered internally and externally. Whensteel plate (black plate) is employed, to avoid use of tin and otherprotective metals, difllculty is encountered in preserving the sheetagainst corrosion prior to fabrication-into the container element, andpreserving the element prior to and after filling with the packagedmaterial. For many such employments, as the element is not heated incontact with the product, a protective coating over the steel plate willbe satisfactory if it is cheap, easily applied, and permits thefabrication to be conducted without special operations. The employmentof the usual lacquers or enamels, however, gives difficulty because suchprotective coatings when applied over areas to be soldered during thefabrication, have interfered with eflicient solder-bonding of thecontainer seams. In order to overcome this difficulty, it has beennecessary heretofore to exercise great care in avoiding application ofthe protective coatings at the edge portions intended to be formed intoseams and solder-bonded, or to provide all-over protective coatings andthen resort to means for removing the coatings from the edge portionsintended to be formed into seams and solder-bonded. Thes edge-preparingsteps naturally consume a considerable amount of time and labor and areobjectionable because they are wasteful. It is, therefore, a purpose ofthe present invention to provide a novel method of preparing coatedcontainer elements which will avoid the objections noted by the.provision of all-over protective coatings capable of providing thedesired protection against direct contact of the packaged products withthe metallic walls of the can bodies and yet permitting solder-bondingof the seams without resort to the wasteful edgepreparation stepshereinabove mentioned.

Another object of the invention is to provide can blanks which includeall-over protective coatings which will protect the blanks againstoxidation by the atmosphere and insulate products packaged in cans madefrom the. blanks against direct contact with the metallic walls of thecans and which coatings have a flux directly incorporated therein whichwill aid in effecting.an efllcient solder-bonding, that is, permitsolder-bonding without use of a flux other than that directly embodiedin the coating.

With the above and other objects in view that will hereinafter appear,the nature of the invention will be more fully understood by followingthe detailed description, the appended claim, and the several viewsillustrated in the accompanying drawing.

In the drawing:

Figure l is a perspective view diagrammatically illustrating the step ofcoating the blanks or sheets.

Figure 2 is a sectional view diagrammatically illustrating the step ofbaking the coated blanks or sheets.

Figure 3 is a sectional view somewhat diagrammatically illustrating thestep of forming can bodies and the side seams thereof from the allovercoated blanks.

Figure 4 is a sectional view diagrammatically illustrating the step ofsolder-bonding the side seams.

In the practice of the invention, a can element or blank is preparedfrom steel plate, by coating the original sheet or the blanks formedtherefrom with a protective coating which permits direct solder-bondingwithout prior removal of the coating, and which is eflective inassisting the solderbonding operation.

Such coatings are composed of two basic ingredients for providing thefilm residue, being (1) a lacquer which provides a non-heat-hardeningfilm that is thermo-fusible at soldering temperature and has thecharacteristic of being dry, hard, tough, cohesive, impermeable, andadherent, (2) a fluxing agent which is liquid and effective upon themetal at the soldering temperature and is preferably a solid at theordinary temperature, and is capable of intimate incorporation into thelacquer base so that with its pres- .ence the coating film has thedesired characteristics and so that, upon thermofusion and latercooling, the coating is reconstituted to cover the plate. Theseingredients are applied in the form of a, conjoint solution.

As one example of practice of the invention, such a coating film isprepared from a solution of a vinylal resin. 22 parts by weight of vinylbutyral polymer resin of th type commercially known as YSG is blendedwith 7 /2 parts of WW rosin in a solvent for these substances, which maybe an ester or ketone with or without a hydrocarbon diluent solvent;parts of butyi cellosolve are satisfactory for the purpose. Thi lacquersolution is applied as an all-over protective coating on the blankplate, and is then baked at 325 degrees F. These coating and bakingsteps are diagrammatically illustrated in Figures 1 and 2 of thedrawing. While Figure 1 illustrates a spray coating step, it is to beunderstood that this is illustrative of the application and that thecoating may be applied by rollers, dipping, ilooding, or other method.The coating may be applied to the can elements which have already beencut for size, but preferably the application ismade to the large sheetsof steel plate as manufactured and thus serves to prevent corrosionthereof prior to fabrication. The lacquer sheets are later cut into therequired size for the blanks, and in the case of can bodies may beformed on the usual body maker as indicated by Flgur e 3 of the drawing,and the solder applied for the solder-bonding operation at the side seamof-the can body as diagrammatically illustrated on Figure 4.

In a further example of practice, the can body blanks are given anall-over protective coating comprising 22% parts, by weight, of vinylacetate VYAA resin and 7 parts, by weight, of WW rosin dissolved in 70parts, by weight, of methyl iso-butyl ketone (hexone). This protectivecoating is applied to the individual blanks, or to the sheets, and isthen baked at 325 degrees F. These coating and baking steps arediagrammatically illustrated in Figures 1 and 2 of thedrawing ashereinbefore explained. When the lacquer has been applied to the sheets,the sheets may be stored without danger of corrosion. The sheets aresubsequently cut into individual blank sizes and the blanks, thus cut orindividually formed, can be shaped into bodies and have their side seamseiiiciently solder-bonded without the use of additional flux. Thisformation of the can bodies" and the side seams thereon isdiagrammatically illustrated in Figure 3 of the drawing, as hereinbeforeexplained, and it is to be understood that the solder-bonding of theside seam is accomplished in the manner diagrammatically indicated inFigure 4 without the necessity of including a fluxing step.

The all-over protecting coating herein mentioned is not to be consideredin the most limited sense so as to cover only coatings which are appliedall-over on both faces of a blank or sheet.'I'histermisusedinthebroadersensesoasto include coatings which may beapplied to apart of the area of the face of a can body blank which is tobe exposed internally or externally of a can or to correspondingsurfaces of larser sheets from which such blanks may be cut, or ingeneral to coatings which extend over areas which later are to beprovided with surfacing metal by a heating operation requiring theaction of a flux to assure proper adhesion.

By practicing the invention as hereinabove outlined, it is possible toprovide can elements or blanks having protective coatings which do notinterfere with solder-bonding, and will permit solder-bonding withoutthe use of a flux other than that which is embodied in the protectivecoating.

We claim:

The method of preserving steel plate from corrosion and preparingelements of container bodies therefrom, which comprises applying to thearea of the plate which is to be protected against corrosion an adherentprotective coating which is essentially stable at soldering temperatureand comprising an intimate uniform mixture ofa thermo-fusible andnon-heat-hardening lacquer resin and a thermo-fusible solder fluxingresin, heating a part of the said area to a temperature effective toliquefy the lacquer coating on said area and to melt solder, applyingsolder to the heated partial area wherewith the liquid lacquer isdisplaced from the metal for effecting a bonding of the melted solder tothe metal in the presence of and with a fluxing by the action of thesaid solder flux resin and in the absence of added solder flux andcooling the said partial area wherewlth the lacquer reestablishes a hardprotective film extending over all unsoldered parts of said area.

CURTIS E. MAIER. FRANK J. O'BRIEN.

